I pretty much always use plain text formatting when sending messages, but a couple of my users have brought something to my attention regarding composing messages in HTML format with the Zimbra web client.
When using IE7 and composing a new message in HTML format when the user hits the <CR> it double spaces the text. When the first user brought this to my attention my thinking was that the double spacing was intentional. I told him that word wrap would automatically take effect, and hitting <CR> was basically telling the system that you wanted to start a new paragraph. Then another user asked me "Well what if I want to enter an address?" Since I always use plain text I didn't have an immediate answer. When checking this out I found the "Address" format, which answered my user's question. However, in the process of looking at this I discovered that with the same setup Firefox does not double-space.
I don't know if this is a Zimbra issue, or more of a browser thing, but it does seem a bit inconsistent so I figured I would ask if anyone had any thoughts or ideas on this. From the feedback that I have received I don't think my users like the double spacing.